1. Field of the Invention
The present invention relates to safety closing devices for containers of biological liquids, particularly for test tubes holding blood. The closing devices are comprised of substantially two components: (1) an undercap mounted on the open end of the container, having a bottom of perforable material for allowing the insertion of a drilled rod-shaped element into the container; and (2) a cap, also made of perforable material, mounted on the undercap for assuring the sealed closing thereof.
2. Description of the Prior Art
Closing safety devices comprising a cap and an undercap for the closing of test tubes under vacuum, are known. The purpose of the cap/undercap assembly is to assure both the sealing of the vacuum present in the inside of the container prior to filling and the sealing of liquid that afterwards is introduced therein. To introduce the liquid into the test tube under vacuum, a support device on which is mounted a needle with a double point, the so-called "needle holder", is usually used. One point of the needle is inserted into the part of patient from which it is necessary to extract the liquid, for example, blood, while the other point is inserted through the perforable cap and undercap and extends into the inside of the test tube. Collection of liquid within the test tube by vacuum occurs in this manner without removing the cap and undercap from the test tube. After the suction operation is completed, the test tube is extracted from the needle holder and the needle is extracted from the human body and then removed from the needle holder and disposed of, being of no more use while the above mentioned needle holder can be used for another drawing of liquid from the human body.
The test tube holding the drawn blood sample can then be sent to the laboratory perfectly sealed. During analysis, the cap is usually removed from the undercap to allow the extraction of the liquid from the test tube, using a proper drawing device, such as a pipetting, a tip for a pipette device, or a needle, which perforates and passes through the undercap to enter the inside of the test tube. In particular, if the undercap includes one or many through incisions or slits with flexible edges in its bottom, as described in the European Patent No. 0391461 filed on Mar. 26, 1990, the drawing device crosses through the slits between the flexible edges and, after the removal of the device from the test tube, the edges close together to prevent undesirable leakage of liquid remaining in the test tube. As disclosed in the above-mentioned Italian Patent, the undercap, having the shape of a glass, is pressure-fitted into the opening of the test tube. Similarly, the cap is pressure-fitted into the inside of the undercap. So, the sealing between the undercap and test tube and between the undercap and cap is assured by radial pressure.
Closing devices of this type do not offer sufficient guarantees for a safe closing, because the undercap, coupled with the internal surface of the test tube by only radial pressure, can be accidentally removed from the test tube causing the blood to spill, with a consequent risk of infection to the operator in charge of the drawing operation or handling the test tube. In practice, the undercap can be accidentally disengaged from the test tube by the dragging caused by the cap during its removal, indeed, ageing of the contacting materials of the cap and undercap can produce so strong a coupling that the two components behave as if they are a single piece. Furthermore, the undercap can be accidentally removed from the test tube when the pipette or the tip, used for the drawing of the blood sample, is removed from the test tube.
On the other hand, if it is necessary to remove the undercap from the test tube for the purpose of completely opening the mouth of the tube, difficulty may arise when trying to extract the undercap from the test tube, due to the high adhesion that can occur between the undercap and test tube. The increased effort needed to extract the undercap and the sudden release of the undercap from the test tube can cause a spray of blood outward, exposing the operator at risk of contamination through the effect of vaporization and/or aerosol formation of the blood.
Naturally, even when the test tube is filled at normal room pressure and then closed again by the known closing devices, removal of the undercap can occur for example, during its transport due to accidental contacts or expansion of internal gases. In any case, when the undercap is removed, it can be contaminated with blood and therefore represents a high risk, both for resting the undercap in any place without causing pollution to the environment and for handling the undercap for repositioning the same on the container, if it is necessary to close the container again.
Further, the re-closing by the known closing devices requires the insertion of the cap into the undercap. This operation is difficult due to the air present in the cavity of the undercap, which hinders cap insertion.
Finally, the above-mentioned closing devices have an undercap which extends inside the container, reducing the utilizable volume of the container.